1. Field of the Invention
The present invention relates to a printer for printing on a sheet. The printer of the present invention is generic name of a device comprising: a sheet sending mechanism which successively sends cut sheets; and a printing mechanism which successively prints characters, graphics, photographic images or the like on the sheets sent by the sheet sending mechanism. Not only a printer with a single function, but also a copying device, a facsimile device, a composite device (or a multifunction device) and the like comprising the sheet sending mechanism and printing mechanism also are the printer described herein.
2. Description of the Related Art
There has been developed a printer which takes a piece of sheet from a cassette having a plurality of cut sheets stacked thereon, sends the sheet to a printing region via a sheet guide, and prints on the sheet while the sheet passes through the printing region.
There has been developed a printer in which a pair of feed-in rollers is disposed on an upstream side of the printing region in order to send a sheet so that it passes through the printing region.
When sending a cut sheet with the pair of feed-in rollers, it is preferable that a plurality of cut sheets are successively sent by the pair of feed-in rollers in a relationship that a small space is formed between the back edge of a previously sent sheet and the front edge of a subsequently sent sheet. If this space is not formed and the back edge of the preceding sheet (previously sent sheet) overlaps with the front edge of the subsequent sheet (subsequently sent sheet), an area in which nothing is printed is created. If this space is excessively large, the printing process requires a long period of time.
In order to form the appropriate space between the preceding sheet and the subsequent sheet, Japanese Patent Application Laid-Open Publication No. 2001-301998 (see particularly FIG. 2, FIG. 3, and FIG. 8) proposes a printer which comprises: a sheet supply mechanism for taking one sheet from a cassette and sending the sheet; a sheet feeding mechanism for receiving the sheet, which is sent by the sheet supply mechanism, and sending the sheet to a printing region; and a sheet sensor for detecting an edge of the sheet. In this printer, the sheet supply mechanism starts supplying operation of the subsequent sheet when a predetermined time has elapsed since the front edge of the preceding sheet was detected by the sheet sensor. By this printer, the space is formed between the back edge of the preceding sheet and the front edge of the subsequent sheet when the sheets pass through the sheet feeding mechanism.